Get the most accurate measurements using your Apple Watch

Your Apple Watch uses the personal information that you provide to help calculate metrics for your daily activity. You can further improve its accuracy using these tips.

Keep your personal information up to date

Your Apple Watch uses your personal information — such as your height, weight, gender, and age — to calculate how many calories you burn and more.

To update your personal information, open the Apple Watch app on your iPhone. Tap the My Watch tab, then tap Health. Tap Edit, then tap the item that you want to change.

Make sure that you earn Move and Exercise credit

Every full minute of movement that equals or exceeds the intensity of a brisk walk counts toward your daily Exercise and Move goals. For wheelchair users, this is measured in brisk pushes. Any activity below this level counts only toward your daily Move goal.

To make sure that you earn Exercise credit during walks, allow the arm with your Apple Watch to swing naturally. For example, while walking your pet, let the arm with your watch swing freely while the other holds the leash.

If you need both hands while walking, for example to push a stroller, you can still earn Exercise credit with the Workout app. Open the app on your Apple Watch and tap Outdoor Walk. The Activity app relies on arm motion and an accelerometer to track movement, but the Workout app can use the accelerometer, the heart rate sensor, and GPS.

If you turn on Power Saving Mode during a walking or running workout, the heart rate sensor turns off. To turn off Power Saving Mode, open the Apple Watch app on your iPhone, then tap Workout > Power Saving Mode.

If you turn off Heart Rate in Privacy settings, you also won't get a heart rate measurement. To turn on Heart Rate, open the Apple Watch app on your iPhone, then tap Privacy > Heart Rate.

Choose the best workout

When you use the Workout app, choose the option that best matches what you’re doing. For example, if you're running on a treadmill, choose Indoor Run. If you're doing a workout that isn't listed, like strength training, choose Other.

What else affects your heart rate reading

Many factors can affect the performance of the Apple Watch heart rate sensor. Skin perfusion (or how much blood flows through your skin) is one factor. Skin perfusion varies significantly from person to person and can also be impacted by the environment. If you’re exercising in the cold, for example, the skin perfusion in your wrist might be too low for the heart rate sensor to get a reading.

Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings.

Motion is another factor that can affect the heart rate sensor. Rhythmic movements, such as running or cycling, give better results compared to irregular movements, like tennis or boxing.

If you’re not able to get a consistent reading because of any of these factors, you can connect your Apple Watch wirelessly to external heart rate monitors such as Bluetooth chest straps. Learn how to pair Bluetooth accessories.